Physician’s guide, Overview, Signal conditioning – Welch Allyn Holter System - User Manual User Manual
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Directions for Use
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Physician’s Guide
Overview
The Welch Allyn Holter System performs analysis up for to 48-hour of ECG digital data as
a continuous segment of data. The analysis processing consists of the following sub-
processing components:
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Signal Conditioning.
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QRS Detection and Feature Extraction.
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Clustering.
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Beat Classification.
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Heart Rate Calculation.
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ST Measurement.
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Pattern Determination.
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Strip Determination.
The analysis program consists of two major stages. The first stage, main analysis, is
responsible for QRS detection, classification, feature extraction, and clustering.
The second stage is responsible for pattern, tabulation, and strip determination.
This stage is commonly referred to as a re-compile process. During a full analysis, both
the main analysis and re-compile stages are executed. The full analysis will typically take
two minutes to analyze a 3-channel, 24-hour recording. The Re-compile typically takes
only seconds. The Re-Compile occurs multiple times, usually after the clinician has
performed edits. For instance, if the clinician changes the hookup time to a different hour
or minute, the recompile process would re-tabulate the results based on the new time.
Other edits that could trigger a re-compile include:
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ST Episode threshold changes.
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SVE prematurity threshold changes.
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Pause threshold changes.
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Brady and Tachy threshold changes.
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Form Edits.
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Beat Edits.
Signal Conditioning
The signal processing performed during the analysis is used to remove some of the noise
and artifacts normally found during an ambulatory recording. The following types of noise
and artifacts may occur:
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Drift - gradual baseline wander usually caused by respiration.
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Shift - sudden baseline changes in electrode skin impedance or external contact to
electrode site.
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Rail - amplitude saturation of the signal.
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Continuous noise of a single frequency- usually associated with high electrode
impedance and mains 50 or 60 Hz interference.
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Burst of noise- usually several frequencies mixed together due to electrical signals
from active muscles.
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Spikes- large amplitude shifts of a short duration.
The analysis program applies a collection of several filters to correct for these types of
issues. These filters are optimized for the specific sub-process requirements.